All the other gods were doing it - taking the forms of various animals, creatures, monsters. Old Zeus really blazed a trail with that trick. Why all those Greek chicks would fall for a white bull or white swan or whatever, I can't say. Who looks at a swan and says, "Aww yeah, I want to knock me off a slice of that!", I ask you?
Anyway, cows are so placid. Just a simple creature strolling around on a sunny day and masticating - if you're a rain god, getting some sunshine is a pretty rare treat. So he figures, "Yeah, a cow! That's the life for me! No danger, no stress, no worries - just some rest and relaxation!"
It seemed ideal, at first - just as he imagined. Sunshine! Other cows to chew the cud with! Green Grass! And finally, at long last, dry! His heart welled over with the simple joy of just being - even if just being was bovine and sort of dull. He saw only the best in his fellow cows in the field, even the temperemental old bull on the other side of the fence. He winked slyly at the old bull, letting him know, "Oh yeah pal, I know how heavy it is, all that authority. You're one of my kind - this cow thing, it's just a gig. Just a lark." And all with a wink, because when you're a god, even as non-anthropomorphic a god as the rain god, you can communicate volumes with every wink of your big brown cow-eye, with every peal of thunder, with every patter of a drop on Spring's first unfolding buds.
The rain god was so happy, so full of idiot-bliss that when the cows lined up and startled jostling down a chute, he figured he'd follow along. Everything else had turned out so ideal! The cows disappeared into a building, not unlike the one where every morning they hooked up the throbbing machine that massaged his teats. Whatever it was in there, it must be good, right?
Yeah well. Turns out it was a stun line.
And now, I'm wearing the rain god's hide. I know this, because every time I wear this fucking suede jacket, it rains.
Even in Los Angeles. And it never rains in Los Angeles.